1. Field of the Invention
The present invention relates to a liquid-jet head unit including a liquid-jet head for injecting a liquid and a liquid-jet apparatus, and particularly relates to an ink jet recording head unit including an ink jet recording head for ejecting ink as the liquid and an ink jet recording device.
2. Background art
An ink jet recording device, such as an ink jet printer or an ink jet plotter includes an ink jet recording head unit (hereinafter, referred to as a head unit) including an ink jet recording head capable of ejecting, as ink droplets, ink reserved in an ink reservoir portion of an ink cartridge or an ink tank.
The head unit includes: an ink jet recording head including nozzle lines, each of which is formed of nozzle orifices arranged in parallel lines; a head case fixed to ink supply ports side of the ink jet recording head; and a cover head protecting an ink-droplet ejecting surface side of the ink jet recording head.
Since the head case of the head unit as described above is generally formed of a resin material such as plastic, there is a problem that, due to a difference in linear expansion coefficients between the head case and a single crystal silicon substrate constituting the ink jet recording head, the head case warps due to a temperature change. Particularly when the warpage occurs in a direction, in which the nozzle orifices are arranged in parallel lines, impact positions which ink droplets impact on a recording medium such as a sheet of paper are displaced. Accordingly there is a problem that printing quality is deteriorated.
Additionally, since the direction, in which the lines of nozzle orifices are arranged in parallel lines, is generally a longitudinal direction of the ink jet recording head, the ink jet recording head warps in a manner that the nozzle plate side becomes convex in the longitudinal direction. As a result, there is a problem that a nozzle plate and a passage-forming substrate are separated.
Furthermore, although the warpage of the ink jet recording head is prevented if the head case is formed of a single crystal silicon substrate or a ceramic which has the same linear expansion coefficient as that of the material of the ink jet recording head, such a material is expensive and there arises a problem that costs are increased.
Note that, as a constituting member of an ink jet printer, one using a liquid crystal polymer has been proposed (for example, refer to Japanese Patent Application Laid-open No. 10-86168).
However, in the above patent literature, disclosed is only to mold the constituting member with high precision by reducing a mold shrinkage factor of the member in a longitudinal direction.